If you're a Widget Maker 4 and they're hiring a Widget Maker 5, I would expect that he'd get paid more than you.
But I see your point: employers will offer more to a candidate if they really want the guy based on experience, skills, labor market conditions, etc., but doing that leads to exposure for sex discrimination claims if current employees are paid in a discriminatory manner as a result of this new hire. So, that company would need to upgrade the wage scale to make room for the new guy, and bring everybody else up to keep the wages non-discriminatory. Most employers don't do this.